1. Field of the Invention
This invention relates to an apparatus for and a process of extracting oxygen from fluids in which oxygen is dissolved.
2. Description of the Prior Art
Oxygen is required in many important chemical reactions utilized by humans, the most important being life-supporting respiration. When these reactions are carried out on the surface of the earth, the oxygen content of air is often sufficient to provide enough oxygen for the desired reaction. However, there are many instances when oxygen is required at concentrations higher than those normally present in air. For example, pure oxygen is required in large quantities by the steel industry. Oxygen is used to volatilize carbon and other nonmetal impurities with greater speed and control than would be possible if air alone were used. Persons having lung disorders which interfere with their ability to obtain oxygen from air likewise require purified oxygen for home or hospital use. Miners working in so-called bad air, i.e., air of less than normal oxygen content, require bottled oxygen at present. Oxygen has proven highly efficient for the treatment of liquid effluents in sewage. Incineration of wastes in closed systems using pure oxygen has become an important method for disposing of toxic wastes.
Although various preparative methods exist for producing oxygen on a small scale, oxygen is generally prepared by the fractional distillation of liquid air when it is required in large quantities. Typically, filtered air is passed through an alkali absorbant in order to remove moisture and carbon dioxide. The air is then compressed, and the heat of compression is removed by ordinary cooling procedures. The cooled and compressed air is then allowed to expand, taking advantage of the fact that a compressed gas cools as it expands. The compressed gas is then recompressed, cooled, and expanded again multiple times in order to finally produce liquified air. The liquid air is allowed to warm in order to boil off nitrogen and other light impurities, leaving liquid oxygen. The liquid oxygen may be stored in that form or as compressed gaseous oxygen.
Although this process produces oxygen in a commercially useful form, it is a process which requires a large immovable plant and a delivery system for transporting either cryogenic liquid oxygen or compressed gas. While the oxygen distribution system has worked well for the steel industry, there are many applications where local production of oxygen would be useful. For example, home or hospital generators of oxygen would be extremely useful for persons afflicted with breathing disorders. Even large consumers of oxygen, such as the steel industry, would benefit by a process which reduces the energy requirements of producing oxygen from air by liquification.
Furthermore, one of the primary problems which hinders man in his efforts to explore and develop the ocean realms is the lack of a ready supply of oxygen. In most of the world's oceans, the oxygen content of both shallow and deep waters is similar to that of surface water in equilibrium with air. Practical methods have not yet been devised for extracting and utilizing this vast amount of oxygen for the maintenance of man in an undersea environment. Fish, however, have obviously solved the problem of oxygen extraction from seawater. Fish species weighing well over a thousand pounds and burning metabolities at rates roughly comparable to that of man easily extract adequate dissolved oxygen from seawater for their varied activities. Moreover, many species of fish transfer oxygen from seawater into a gaseous state. These fish, ones that possess swim bladders, are able to pump and concentrate oxygen against enormous hydrostatic pressure gradients. In certain fish species oxygen is transported from the dissolved state in seawater, with a .sub..rho. O.sub.2 of 0.2 atmospheres, to a gaseous phase in the swim bladder where the .sub..rho. O.sub.2 may exceed 100 atmospheres.
Many attempts to develop methodologies of extracting oxygen from gaseous mixtures or water are known. Warne et al, U.S. Pat. No. 2,217,850, and Folger et al, U.S. Pat No. 2,450,276, disclose processes of separating oxygen from other gases using solutions of cobalt compounds. However, these techniques would be ineffective in a liquid system, e.g., seawater, since the compounds are in solution and would be washed away if contacted with liquids rather than the disclosed gases. Miller, U.S. Pat. No. 3,230,045, discloses using oxygen-binding chromoproteins such as hemoglobin and hemocyanin to separate oxygen from other gases. The chromoproteins are kept moist or in solution and are immobilized on filter paper where they may be bound by a binder such as fibrin; an electrolyte such as sodium chloride may also be present. However, this technique would also be ineffective in a liquid system since the protein is not insoluble and thus would be washed away if water were allowed to flow through the system. Moreover, there is no provision for regeneration of oxidized (inactive) oxygen carriers that would be formed in this system. Bodell, U.S. Pat. No. 3,333,583, and Robb, U.S. Pat. No. 3,369,343, disclose apparatus for extracting oxygen from seawater using thin tubes of silicone rubber or a membrane of silicone rubber, respectively. However, neither the capillary networks nor the permeable membranes working alone have been found to be practicable in real-life situations. Isomura, U.S. Pat. No. 3,377,777, discloses concentrating oxygen from natural waters by equilibration with exhaled gases, i.e., by utilizing large areas of gas-water interface and simple diffusional considerations such that the partial pressure of the gas phase and the partial pressure of the liquid phase in the extraction zone provide for release of oxygen from the liquid phase into the gas phase and absorption of CO.sub.2 by the water phase. Additionally, the solubility of oxygen in seawater is decreased by heating the seawater, and this heating also increases the solubility of CO.sub.2. However, the requirement of heating the seawater results in an energetically undesirable process. Rind, U.S. Pat. No. 4,020,833, discloses an oxygen source for closed environments comprising a mixture of a metallic superoxide, which releases oxygen upon contact with CO.sub.2 and water vapor, and a material which absorbs CO.sub.2. However, this system suffers from the defect of the capacity being limited by the bulk amount of mixture which can be carried, i.e., it is not capable of continuously producing oxygen without replenishment. Iles et al, U.S. Pat. No. 4,165,972, discloses separating oxygen from gas mixtures using metal chelates as sorbents. However, the technique is not extendable to the extraction of oxygen from water.
Many compounds in solution have been examined with respect to their oxygen absorption properties and the mechanistics thereof. The properties of hemoglobins, hemerythrins and hemocyanins, the naturally occurring oxygen carriers, have been the subject of numerous studies, as documented in Bonaventura et al, J. Am. Zool., 20, 7 (1980) and 20, 131 (1980). Artificial oxygen carriers and their properties in solution are described by a number of researchers. Traylor et al, "Solvent Effects on Reversible Formation and Oxidative Stability of Heme-Oxygen Complexes", J.A.C.S. 96, 5597 (1974) discloses the effect of solvent polarity on oxygenation of several heme-base complexes prepared by reduction with sodium dithionite or a mixture of Pd black and calcium hydride. Crumbliss et al, "Monomeric Cobalt-Oxygen Complexes", Science, 6, June 1969, Volume 164, pp. 1168-1170, discloses Schiff base complexes of Co(II) which form stable cobalt-oxygen species in solution instead of cobalt-oxygen-cobalt bridged complexes. Crumbless et al, "Monomeric Oxygen Adducts of N,N'-Ethylenebis (acetylacetoniminato) ligandcobalt(III): Preparation and Properties", J.A.C.S. 92, 55 (1970), discloses a series of monomeric molecular oxygen carriers based on cobalt ligand complexes. Dufour et al, "Reaction of Indoles with Molecular Oxygen Catalyzed by Metalloporphyrins", Journal of Molecular Catalysis, 1, 277 (1980), discloses the catalysis of the oxygenation of simple, alkylsubstituted indoles by Co(II), Co(III), and Mn(III) meso-tetraphenyl-porphines wherein a ternary complex O.sub.2 -CoTPP-indole is formed initially. Brault et al, "Ferrous Porphyrins in Organic Solvents: I. Preparation and Coordinating Properties", Biochemistry, 13, 4591 (1974), discloses the preparation and properties of ferrous deutereporphyrin dimethyl ester and ferrous mesotetraphenylporphine in various organic solvents. Chang et al, "Kinetics of Reversible Oxygenation of Pyrroheme-N-[3-(1-imidazolyl)propyl]amide", discloses studies on the oxygenation of pyrroheme-N-[ 3-(1-imidazolyl)propyl]amide, i.e., a synthesized section of the myoglobin active site. Castro, "Hexa and Pentacoordinate Iron Poryhyrins", Bioinorganic Chemistry, 4, 45-65 (1974), discloses the direct synthesis of hexa and pentacoordinate iron porphyrins, i.e., the prosthetic groups for the active sites of certain cytochrome and globin heme proteins. Chang et al, "Solution Behavior of a Synthetic Myoglobin Active Site", J.A.C.S., 95, 5810 (1973), discloses studies on a synthesized section of the myoglobin active site and indicates that the oxygen binding reaction does not require the protein Naturally occurring oxygen carriers have been chemically cross-linked and their properties described. Bonsen et al, U.S. Pat No. 4,053,590, discloses a polymerized, cross-linked, stromal-free, hemoglobin proposed to be useful as a blood substitute. Morris et al, U.S. Pat No. 4,061,736, discloses intramolecularly cross-linked, stromal-free hemoglobin. Wong, U.S. Pat. No. 4,064,118, discloses a blood substitute or extender prepared by coupling hemoglobin with a polysaccharide material. Mazur, U.S. Pat. No. 3,925,344, discloses a plasma protein substitute, i.e., an intramolecular, cross-linked hemoglobin composition.
Numerous papers have been published on immobilization of hemoglobin and its functional consequences, but not in connection with processes for efficient oxygen extraction from fluids. Vejux et al, "Photoacoustic Spectrometry of Macroporous Hemoglobin Particles", J. Opt. Soc. Am., 70, 560-562 (1980), discloses glutaraldehyde cross-linked hemoglobin and its functional properties. The preparation is described as being made up of macroporous particles. Hallaway et al, "Changes in Conformation and Function of Hemoglobin and Myoglobin Induced by Adsorption to Silica", BBRC, 86, 689-696 (1979), discloses that hemoglobin adsorbed on silica is somewhat different from hemoglobin in solution. The adsorbed form is not suitable for 0.sub.2 extraction from liquids. Antonini et al, "Immobilized Hemoproteins", Methods of Enzymology, 44, 538-546 (1976), discloses standard immobilization techniques as applied to hemoglobin and their functional consequences. Mention is made of hemoproteins bound to cross-linked insoluble polysaccharides such as Sephadex or Sepharose, using a pre-activation of the resin with CNBr. Rossi-Fanelli et al, "Properties of Human Hemoglobin Immobilized on Sepharose 4B", Eur. J. Biochemistry, 92, 253-259 (1978), discloses that the ability of the hemoglobin to be bound to Sepharose 4B is dependent upon the conformational state of the protein. Colosimo et al, "The Ethylisocyanate (EIC) Equilibrium of Matrix-Bound Hemoglobin", BBA, 328, 74-80 (1973), discloses Sephadex G-100, Sephadex DEAE-A50 and Sephadex CM-C50 as supports for human hemoglobin insolubilization. The paper shows that the affinity of the insolubilized protein for EIC is increased relative to that in solution. Lampe et al, "Die Bindung von Sauerstoff an tragerfixiertes Hamoglobin", Acta Biol. Med. Germ., 33, K49-K54 (1974), discloses studies on CM-Sephadex insolubilized hemoglobins. Lampe et al, "Der EinfluB der Immobilisierung von Hamoglobin auf dessen Sauerstoffindung", Acta Biol. Med. Germ., 34, 359-363 (1975), discloses studies on CM-Sephadex insolubilized hemoglobins. Pommerening et al, "Studies on the Characterization of Matrix-Bound Solubilized Human Hemoglobin", Internationales Symposium uber Struktur und Funktion der Erythrezyten (Rapoport and Jung, ed.), Berlin Akademie-Verlag Press, 179-186 (1975), discloses Sepharose-Sephadex types of insolubilization. Brunori et al, "Properties of Trout Hemoglobin Covalently Bound to a Solid Matrix", BBA, 494(2), 426-432, discloses Sepharose 4B or Sephadex G-200, activated by CNBr, to immobilize the hemoglobin. Some changes in the functional properties of the hemoglobin were found.
Various techniques for the insolubilization (or immobilization) of biological materials have been developed, though not described in conjunction with insolubilization and utilization of oxygen carriers. Stanley, U.S. Pat. No. 3,672,955, discloses a technique for the preparation of an insoluble, active enzyme, a biological catalyst, wherein an aqueous dispersion of the enzyme is emulsified with an organic polyisocyanate, mixed with a solid carrier and the volatile components are then evaporated from the mixture. Wood et al, U.S. Pat. No. 3,928,138, discloses a method of preparing a bound enzyme wherein, prior to foaming, an isocyanate-capped polyurethane is contacted with an aqueous disperson of enzyme under foam-forming conditions, whereby polyurethane foams containing integrally bound enzyme are obtained. Unsworth et al, U.S. Pat. No. 3,928,230, discloses the encapsulation of fluids and solids by dissolving a water-insoluble polymerizable epoxy monomer in a solvent having high affinity for water; dispersing the monomer solution in water; dispersing in the so-formed aqueous dispersion the substance to be encapsulated; adding a polymerizing agent in a solvent having a higher affinity for water than for the polymerizing agent; and polymerizing until polymerization of the monomer is complete. Wood et al, U.S. Pat. No. 3,929,574, discloses an enzyme integrally bound to a foamed polyurethane prepared by, prior to foaming, contacting an isocyanate-capped polyurethane with an aqueous dispersion of enzyme under foam-forming conditions, whereby polyurethane foams containing integrally bound enzyme are obtained. Hartdegen et al, U.S. Pat. No. 4,094,744, discloses water-dispersible protein/polyurethane reaction products formed by admixing a water-dispersible, biologically-active protein and an isocyanate-capped liquid polyurethane prepolymer having a linear polyester backbone under essentially anhydrous conditions to form a solution, said protein and prepolymer reacting to form a watersoluble reaction product wherein the protein and prepolymer are bound together. Hartdegen et al, U.S. Pat. No. 4,098,645, discloses enzymes immobilized by the process of mixing the protein and an isocyanatecapped liquid polyurethane prepolymer in the absence of water; foaming the mixture by reacting it with water to form a polyurethane foam. Huper et al, U.S. Pat. No. 4,044,196, discloses proteins insolubilized using polymers containing maleic anhydride or di- and polymethacrylates. Huper et al, U.S. Pat. No. 3,871,964, discloses proteins insolubilized using polymers containing anhydride, di-methacrylate and a hydrophilic monomer.
Many of the prior art problems were overcome by the invention disclosed in U.S. Pat. No. 4,427,416 and 4,343,715, which disclose oxygen carriers which have been insolubilized at high concentrations by being entrapped and/or covalently linked to a polyurethane matrix or to comparable supports in states that are capable of reversible oxygen bonding and are regenerable in the event of oxidation. The material disclosed in these patents is generally known by the name "Hemosponge", since it is generally, though not necessarily, based on hemoglobin. The method and material as described in these patents are perfectly capable of extracting oxygen from various fluid environments in useful form, but the rate of extraction is less than that which may be desired for many applications which involve a high rate of oxygen use. Accordingly, there remains a need for an improved apparatus and method for the extraction and utilization of oxygen from fluids.